The invention relates to a technology enabling a network to be utilized at a high efficiency by properly designing a route along which nodes relay traffic and also a traffic allocation in the network configured by connecting a plurality of nodes.
The invention is a technology employed for managing and operating, for instance, a virtual LAN service (Example: wide area Ethernet (registered trademark)) for providing multipoint-to-multipoint communications among user sites extending over a plurality of points. To be specific, the invention relates to a technology of determining a route for accommodating user traffic and bandwidth on a user-by-user basis to attain highly-efficiency accommodation while ensuring a sufficient speed to such an extent as not to exceed a subscribed bandwidth of a connection line (access link) between the user site and a relay network in a virtual LAN operation system.
As a service for providing the multipoint-to-multipoint communications between the plurality of user sites, there have hitherto been broadly known a so-called wide area Ethernet service and TLS (transparent LAN service), wherein Ether switch nodes are disposed in the relay network, and the user traffic is accommodated by use of an Ethernet VLAN technology. Hereinafter, the discussion will be made by exemplifying the wide area Ethernet.
In the wide area Ethernet accommodating multipoint LANs, a common carrier for providing services determines routes (tree topology) that connect all the user sites to be connected each other, and allocates the routes as a logical broadcast domain (VLANs) to the users. At this time, a transferable VLAN and an untransferable VLAN are set per output port in the Ether switch nodes. This enables determination of a reachable range of the user traffic, whereby a traffic sent from a site of a user A can be prevented from reaching a site of a different user B by allocating a different VLAN to every user. Namely, the same network is capable of accommodating a plurality of different user traffics.
Herein, an aggregation of the nodes or links included in the logical broadcast domain allocated to a certain user is referred to as a route, and a process of determining a range of the logical broadcast domain is called a route design. This route design involves, specifically, determining which port the traffic is made transferable at and which port the traffic is made untransferable at in each of the nodes on the relay network, and determining bandwidth to be allocated to each of these ports.
The VLAN allocation to the user traffic is actualized by attaching, for example, a VLAN tag defined in IEEE802.1Q to each Ethernet frame sent by the user at an ingress node of the relay network. The tag contains an identifier (VLANID) for identifying the traffic.
Supposing that the VLANID for the user A is determined to be, e.g., No. 100 (a process of determining what number of VLANID is assigned and which user is assigned the VLANID, is done by, for example, an operator who properly determines a unique value that is not overlapped with those of other users), VLANID 100 is written into the VLAN tag of the Ethernet frame of the user A. In an interior of the relay network (including the ingress node of the relay network), a traffic transferable port is determined by seeing this VLANID. It is based on the normal Ethernet technology to determine specifically which port among the transferable ports the traffic is transferred to. Namely, this depends on a destination MAC address contained in each Ethernet frame and on a function of the node (which will hereinafter be also called an Ethernet device).
If the Ethernet device has a MAC address learning function and if a MAC address learning table has an entry of a destination MAC address and a transfer destination port, the frame is forwarded to this port. In the case of the Ethernet frame containing a destination MAC address that is not entered in the MAC address learning table or the Ethernet device that does not have the MAC address learning function, the received frame is copied and thus forwarded (broadcast) to all the transferable ports excluding the receipt port. When the frame is forwarded across the relay network and reaches an egress node of the relay network, the egress node detaches the VLAN tag from the frame and outputs the frame to a port corresponding to this VLANID, thereby completing the traffic transfer to the desired user.
In the wide area Ethernet, it is a main case at the present that the user settles (subscribes) a speed (bandwidth) of an access link for every want-to-connect site with the service provider and is provided (receives) the service. The access link indicates a circuit that connects the site to the relay network. In this case, the user traffic, after being narrowed down to a traffic speed that does not exceed the subscription value in the access link of the site, flows into the relay network. Within the relay network, the traffic is forwarded based on the Ethernet system (the broadcast, the MAC address learning, etc.) within the logical broadcast domain allocated to the user.
It is considered that the user traffic, of which the traffic speed has been narrowed down in the access link, is therefore flowed without being controlled particularly in its bandwidth along the route determined (e.g., manually) by the operator (the service provider) or in a way of its being allocated with bandwidth large enough to accommodate the user traffic (for example, to such an extent as not to cause a conflict in communications performed among all the sites) in the respective links on the route in the relay network. In the latter case, there is allocated simply large bandwidth, e.g., 100 Mbps larger than a sum 90 Mbps of the access link bands of all the sites along the route (FIG. 1), and so on.
Prior arts related to the invention of the present application are technologies disclosed in, for example, the following patent documents 1 through 4.
[Patent Document 1]
Japanese Patent Application Laid-Open Publication No. 9-83546
[Patent Document 2]
Japanese Patent Application Laid-Open Publication No. 11-341154
[Patent Document 3]
Japanese Patent Application Laid-Open Publication No. 2002-141932